Integrated Rate Laws

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AP Chemistry › Integrated Rate Laws

Questions 1 - 5

The half life of a first order reaction is 1.5 hours. What is the rate constant of this reaction?

1.5

0.75

0.52

0.46

0.21

Explanation

$t_{\frac{1}{2}} = \frac{ln2 }{k}$

$k =\frac{ln2}{t_{\frac{1}{2}}} = \frac{ln2}{1.5} = 0.46$

Cyclopentane is unstable and decomposes by a first order reaction. The rate constant for this reaction is 9.5 s-1. What is the half life of the reaction?

0.0314 seconds

0.0582 seconds

0.0614 seconds

0.0729 second

0.132 seconds

Explanation

$t_{\frac{1}{2}}=\frac{ln2 }{k} = \frac{ln2}{9.5} = 0.0729 seconds$

The rate constant for a second-order reaction is 0.15 M-1s-1. If the initial concentration of the reactant is 0.30 M, how long does it take for the concentration to decrease to 0.15 M?

11.1 seconds

22.2 seconds

44.4 second

88.8 seconds

253 second